Remarkable historic timber roofs. Knowledge and conservation practice. PART 1 - Construction history and survey of historic timber roofs

The study of historic timber roof structures has recently reached the widespread dissemination it deserves within the scientific community, considering its relevance for the more general issues of use, conservation, and safety of the built heritage. The function of covering and protecting large spaces without intermediate supports (e.g., theatres, halls, church naves, factories, and warehouses) has been implemented using construction types of considerable ingenuity even more than static analysis. The outcomes are often unique in their kind and based on the wisdom and competence of engineers, architects, and master carpenters, who made their advancements following cultural, technical-scientific, and socio-economic factors. The conservation of these valuable carpentry works for their safety poses interesting challenges since it is never trivial to operate on artifacts built in the context of extinct or radically evolved technical cultures. Their modifications over time, their state of conservation as well as the interaction with the rest of the building are often unknown and not easily predictable. The “culture of timber structures” has its roots dating back to the origins of the history of construction and extends its branches to the industrial era when it was associated with andthen substantially replaced by the “culture of metal structures”. This phenomenon crossed all of Europe, developing particular specificities in different geographical areas, but also became characteristic of other parts of the world. Today timber roofs represent a fragile heritage threatened by natural and anthropic actions, but they are mainly the subject of fragmentary and episodic research activities, often dictated by the occurrence of fires, collapses, damage, or imminent dangers. This special issue helps to outline the current international panorama of research on historic timber roof structures, especially those with great span or peculiar technical relevance.